Our main goal is to develop new radioligands to be used for neuroimaging and the clinical routine patient studies by SPECT. During this period we were still in a collaborative effort with NIDDK in Bethesda with two different laboratories: Dr. Kenner Rice and Dr. Kenneth A. Jacobson to develop ligands for neuroimaging by SPECT. We developed a new adenosine ligand with Dr. Jacobson. The binding assay indicated that the ligand binds to the brain tissue In Vitro with a high affinity and selectivity. The further study using this ligand after labelled with I-125 indicated that the ligand could not across the blood brain barrier In Vivo in rat. The collaboration with Dr. Flinn is to study the muscarinic receptor subtypes in brain by using [I-125]IQNB. The collaboration with Dr. Bowen is to study the sigma subtypes using our sigma ligands and the collaboration with Dr. Zeeberg is to study the autoradiography in rats using [I-125]IQNB. The collaboration with Dr. Strijckmans is to develop an exchange method from the tributylstannyl precursor QNB to PET Br-QNB ligand for PET studies. During this period, we developed a new adenosine receptor ligand precursor. Radioiodination method with high radiolabelling yield was developed for this ligand. The radiochemical yield for this ligands was > 70% for 5 minutes at room temperature. Autoradiography was performed using this ligand. We developed a new method to radiobrominate the QNB from tributylstannyl precursor QNB for PET studies in France. 125I or123I -sigma ligands were prepared for binding assays, tissue culture studies, and SPECT imaging in primates in order to further the understanding of the ligands. 123I-BetaCIT has been prepared for SPECT studies on alcoholic patients and primates to study the serotonine and dopamine receptors in the brain. The radiochemical yield of 123I-betaCIT is > 70% at room temperature within 5 minutes reaction time. 123IQNB, 123I-betaCIT and 123IBZM ligands were prepared to study the muscarinic receptors, serotonin and dopamine receptors, and D-2 receptors of patients routinely by SPECT.